Epoch J2000 Equinox J2000
|Right ascension||03h 24m 19.37009s|
|Declination||+49° 51′ 40.2455″|
|Apparent magnitude (V)||1.806|
|Spectral type||F5 Ib|
|U−B color index||+0.38|
|B−V color index||+0.483|
|Radial velocity (Rv)||–2.04 km/s|
|Proper motion (μ)||RA: +23.75 mas/yr
Dec.: -26.23 mas/yr
|Parallax (π)||6.44 ± 0.17 mas|
|Distance||510 ± 10 ly
(155 ± 4 pc)
|Absolute magnitude (MV)||–5.1|
|Mass||8.5 ± 0.3 M☉|
|Radius||68 ± 3 R☉|
|Surface gravity (log g)||1.90 ± 0.04 cgs|
|Temperature||6,350 ± 100 K|
|Metallicity [Fe/H]||–0.02 dex|
|Rotational velocity (v sin i)||20 km/s|
Alpha Persei (Alpha Per, α Persei, α Per) is the brightest star in the northern constellation of Perseus, just outshining the constellation's best known star, Algol. Known by the traditional names Mirfak and Algenib, it is a circumpolar star when viewed from the latitude of New York City or higher. It has an apparent visual magnitude of 1.8, placing it among the brightest stars in the sky. Mirfak lies in the midst of a cluster of stars eponymously named the Alpha Persei Cluster, or Melotte 20, which is easily visible in binoculars and includes many of the fainter stars in the constellation. The distance to this star has been determined using the parallax technique, putting it 510 light-years (160 parsecs) away.
The spectrum of Alpha Persei matches a stellar classification of F5 Ib, revealing it to be a supergiant star in the latter stages of its evolution. It has a similar spectrum to Procyon, though the latter star is much less luminous. This difference is highlighted in their spectral designation under the Yerkes spectral classification, published in 1943, where stars are ranked on luminosity as well as spectral typing. Procyon is thus F5 IV, a subgiant star. Since 1943, the spectrum of Alpha Persei has served as one of the stable anchor points by which other stars are classified.
Mirfak has about 8.5 times the Sun's mass and has expanded to roughly 60 times the size of the Sun. It is radiating 7,000 times as much luminosity as the Sun from its outer atmosphere at an effective temperature of 6,350 K, which creates the yellow-white glow of an F-type star. In the Hertzsprung–Russell Diagram, Mirfak lies inside the region in which Cepheid variables are found. It is thus useful in the study of these stars, which are important standard candles.
Etymology and cultural significance
- The names Mirfak and Algenib are Arabic in origin. The former, meaning 'Elbow' and also written Mirphak, Marfak or Mirzac, comes from the Arabic Mirfaq al-Thurayya, while Algenib, also spelt Algeneb, Elgenab, Gęnib, Chenib or Alchemb, is derived from الجنب al-janb, or الجانب al-jānib, 'the flank' or 'side'. Gamma Pegasi also bears the name Algenib.
- Hinali'i is the name of the star in Native Hawaiian astronomy. The name of the star is meant to commemorate a great tsunami and mark the beginning of the migration of Maui. According to some Hawaiian folklore, Hinali'i is the point of separation between the Earth and the sky that happened during the creation of the Milky Way.
- Assemani alluded to a title on the Borgian globe, Mughammid (مغمد), or Muliammir al Thurayya (ملىمرٱلطرى), the Concealer of the Pleiades, which, from its location, may be for this star.
- This star, together with δ Per, ψ Per, σ Per, γ Per and η Per, has been called the Segment of Perseus.
- In Chinese, 天船 (Tiān Chuán), meaning Celestial Boat, refers to an asterism consisting of α Persei, η Persei, γ Persei, ψ Persei, δ Persei, 48 Persei, μ Persei and HD 27084. Consequently, α Persei itself is known as 天船三 (Tiān Chuán sān, English: the Third Star of Celestial Boat.)
- van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357
- Lyubimkov, Leonid S.; et al. (February 2010), "Accurate fundamental parameters for A-, F- and G-type Supergiants in the solar neighbourhood", Monthly Notices of the Royal Astronomical Society 402 (2): 1369–1379, arXiv:0911.1335, Bibcode:2010MNRAS.402.1369L, doi:10.1111/j.1365-2966.2009.15979.x
- Arellano Ferro, A. (October 2010), "Functional relationships for T_eff and log g in F-G supergiants from uvby-beta photometry", Revista Mexicana de Astronomía y Astrofísica 46: 331–338, arXiv:1007.0771, Bibcode:2010RMxAA..46..331A
- Johnson, H. L.; et al. (1966), "UBVRIJKL photometry of the bright stars", Communications of the Lunar and Planetary Laboratory 4 (99): 99, Bibcode:1966CoLPL...4...99J
- Mermilliod, J. C.; Mayor, M.; Udry, S. (July 2008), "Red giants in open clusters. XIV. Mean radial velocities for 1309 stars and 166 open clusters", Astronomy and Astrophysics 485 (1): 303–314, Bibcode:2008A&A...485..303M, doi:10.1051/0004-6361:200809664
- Nordgren, Tyler E.; et al. (December 1999), "Stellar Angular Diameters of Late-Type Giants and Supergiants Measured with the Navy Prototype Optical Interferometer", The Astronomical Journal 118 (6): 3032–3038, Bibcode:1999AJ....118.3032N, doi:10.1086/301114
- Gray, R. O.; Graham, P. W.; Hoyt, S. R. (April 2001), "The Physical Basis of Luminosity Classification in the Late A-, F-, and Early G-Type Stars. II. Basic Parameters of Program Stars and the Role of Microturbulence", The Astronomical Journal 121 (4): 2159–2172, Bibcode:2001AJ....121.2159G, doi:10.1086/319957
- Bernacca, P. L.; Perinotto, M. (1970), "A catalogue of stellar rotational velocities", Contributi Osservatorio Astronomico di Padova in Asiago 239 (1), Bibcode:1970CoAsi.239....1B
- Allen, R. H. (1963). Star Names: Their Lore and Meaning (Reprint ed.). New York: Dover Publications Inc. p. 331. ISBN 0-486-21079-0. Retrieved 2012-09-04.
- Kaler, James B., "Mirfak", Stars (University of Illinois), retrieved 2012-03-14
- Ramanamurthy, G. (2007), Biographical Dictionary of Great Astronomers, Sura Books, p. 167, ISBN 81-7478-697-X
- Garrison, R. F. (December 1993), "Anchor Points for the MK System of Spectral Classification", Bulletin of the American Astronomical Society 25: 1319, Bibcode:1993AAS...183.1710G, retrieved 2012-02-04
- Mérand, Antoine; et al. (August 2007), "Extended Envelopes around Galactic Cepheids. III. Y Ophiuchi and α Persei from Near-Infrared Interferometry with CHARA/FLUOR", The Astrophysical Journal 664 (2): 1093–1101, arXiv:0704.1825, Bibcode:2007ApJ...664.1093M, doi:10.1086/518597
- Davis Jr., G. A. (October 1944), "The Pronunciations, Derivations, and Meanings of a Selected List of Star Names", Popular Astronomy 52 (3): 14, Bibcode:1944PA.....52....8D
- "Astronomer charts skies in Hawaiian" (PDF), Mālamalama, the Magazine of the University of Hawai'i System 29 (2), May 2004: 8, retrieved 2012-03-14
- (Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 11 日